With latest STM (Scanning Tunneling Microscope), AFM (Atomic Force Microscope), and other SPM (Scanning Probe Microscope) techniques, one is able to make measurements and manufacturing even on a nanometer scale. Among SPMs, a near-field microscope which is able to detect optical characteristics in a tiny area below a diffraction limit is used in measurements and evaluations in biotechnology and other fields. Additionally, research and development are being made of optical recording devices and fine-manufacturing device employing the above technique of the near-field microscope.
In the near-field microscope, a fine structure of a size below the diffraction limit is used as a probe, and a front end of the probe is illuminated to generate near-field light in proximity of the front end of the probe. If the probe is driven to scan the surface of a sample under this condition, the near-field light is scattered due to the electric-magnetic interaction between the near-field light localized in proximity of the probe and the surface of the sample, or the near-field light transmits through the sample. By detecting the scatted near-field light or the near-field light transmitting through the sample, it is possible to obtain optical information of the sample surface, such as light intensity, spectrum, and polarization.
In the near-field microscope, usually, the optical probe includes an optical fiber having a core and a clad layer around the core; the core has a sharpened end which is projecting out from an end of the fiber, thus forming a projecting portion of the optical probe, and, for example, the projecting portion is covered by Au, Ag, or other metals. With such an optical probe, it is possible to obtain an optical image having resolution higher than the light wavelength.
When measuring material properties in a small area of the sample by using the above near-field optical microscope, the shape of the sample can be measured by detecting evanescent light localized in a tiny area of the sample smaller than the light wavelength. Then, the evanescent light, which is generated when the sample is illuminated by light under conditions of total reflection, is scattered by the above optical probe, thus, being converted into scattered light. The scattered light is guided into the core of the optical fiber through the projection portion, and is detected by a detector connected to the other end (emission end) of the optical fiber. Namely, the near-field optical microscope scatters the light and detects the scatted light with the optical probe.
In the related art, although the near-field optical microscope is capable of measurements at high resolution, it suffers from a problem in that the coverage of measurements is small, specifically, it is only a few tens micron meters.
Recently, in applications, such as, detect inspections of silicon wafers, it is required that a measurement at high resolution be made by using the near-field light after a measurement in a wide range using ordinarily propagating light is finished so as to measure and inspect the same sample successively. To meet this requirement, a detect inspection device is proposed, for example, in Japanese Laid Open Patent Application No. 2000-55818, in which an optical probe for detection of near-field light is provided in a common optical microscope having an object lens-based observation system.
In the detect inspection device, when measuring certain material properties in a specified tiny area of a wide region covered by the object lens, it is necessary to align the position of the optical probe for the near-field light detection with respect to the tiny area, and then the near-field light detection (high resolution measurement) is made. However, it is very difficult to make the alignment of the optical probe to the tiny area, and the measurement is quite time consuming.